X-ray screen



Dec. 1926.

F. JANUS x-RAY SCREEN Filed April 11. 1924 Patented Dec. 7, 1926.

FRIEDRICH Janus, ormumcgenlnvranx, as srenfon'ro srnnnnsanansxnnrrnnensnmscnerr, or srnnnnssainn'r. nnnn'isnnrrn,.eniaivnanr,,n,:connota-a,`

TION OF GERMANY..

x-nAY sonnen.

Application filed April 1,-1, 1924, serial No. 705,807. ana in Germany'apra 19, 192s.

My invention relates to improvements vin X-ray screens for interceptingthe secondary rays produced in the 'body penetrated by the X-rays andrender-ing -in X-,ray photography the pictures indistinct.

In known screens of this kind flat bars'or' strips of a material which.is almost impervious to X-rays are used, these bars or strips beingarranged edgewise upon a disc-shaped 1G base plate mounted rotatablyaround its centre. The strips are so disposed that they either point tothe centre of rotation or lie spirally around it. In order towpreventthe portions of the X-ray plate situated near the l5 circumference frombeing exposed to Vthe X-rays for longer periods than .those situatednearer the centre, the number of radial bars has been increased towardsthe circumference or the bars have been made wedgeshaped. Bothconstructions'have certain disadvantages, particularly as far as theirmanufacture is concerned. v

It has also been proposed to construct screens of strips of materialimpervious to X-rays and strips of permeable material, which arecombined in layers to form a cylindrical shell. This body is then duringthe exposure rotated around its cylinder axis. Such screens require aconsiderable amount of space between the part of the body exposedV tothe rays and the photographic plate. In the drawing athxed to myspecification and forming part thereof two embodiments of my inventionare illustrated by way of example.

In the drawings is: Fig. 1 a plan of my improved screen, Fig. 2 avertical section along line I I of Fig. l and Y Fig. 3 a plan of aslightly modified construction of the screen.

Similar parts are indicated by the same numerals of reference in all thefigures.

Referring to Figs. l and 2, it will be seen that the screen has theshape of a circular disc l of comparatively small thickness. This discis supported in three grooved rollers 2 disposed around thecircumference.

3. The circumference of the disc is provided with a groove into which acord 4 is placed by means of which and a driving pulley 5 provided witha crank 6 and handle also fixed upon the frame 3 the disc is adapted toThese rollers are iixed upon a suitable frame be rotated.y The `ratio oftransmission of. the cord drive 'is 'suchtfhat the screen disc can berotated withy a comparatively high speed.

The screendisc is composed of `a comparatively large number ofsector-like parts or iieldsi. Each ofthese parts consists in itselfof' a.comparatively large number of strips ofmaterial pervious to X-rays andother strips lof a material impervious to X-J rays. These stripsconsist, for instance, afl- `ternately of lead'foilv and of celluloid,hard paper,bakelite which is aproduct of conden-4 sation of phenol andformaldehyde, or a similar solid' material Vperviousf'to X-rays. Thesestrips are packed very closely together and are either directlycombinedvinto a. soli-d' disc by cementing or pasting'the strips to#such as'the disc 8in F i-g. which also conh sists-of a material perviousto- X-rays and which around its raised edgef) lis provided with thegroove fort'he driving cord 4.' In

gether or they are fixed; upon a base-plate,

the strip composing the individual sectoreach of theviields, the layersor strips of f material pervious to Xfrays alternate with lay-ers ofmaterial substantially impervious to such rays, and all layers of thesame field are parallel to each other, but form an angle with vthedirections of the layers in the neighboring fields.

Although .purely theoretically only one l single strip of the materialimpervious to the X-rays is in both cases situated accurately in thedirection of the radiation emanatingy from the,` X-ray tube, the focusof the tube being assumed to be situated vertically above Vthe centre ofthe disc, theV variations Vof the l shadows caused by the inaccurateposition of the other strips in relation to the X-ray tube, are so smallthat they are no longer perceivable on the X-ray photograph, providedthat the strips and the sectors are made sufficiently narrow. The nindividual sectorother strips ot' the same sector being like parts 7 arepreferably also made of .different Width, as illustrated in Fig. l.

It Will be understood that I do not limit myself to the ldetails ofconstruction described and illustrated by Way of example, but that thesemay be varied in many Ways, which Will easily` suggest themselves tothose skilled in the art Without departing from the spirit of myinvention.

What'I claim as my invention and desire to secure by Letters Patent is:v

l. An X-ray screen consisting of a circular disc built up of a pluralityof sectors composed oilr alternate strips ot a material pervious toX-rays and of a material substantially impervious to X-rays, the centralstrip of each sector disposed radially to said disc and the other stripsparallel to Vsaid central strip, and means for rotating said disc.

2. An X-ray screen consisting of a disc mounted to turn and built up ofa plurality of sectors each comprising a series of spaced strips made ofa. material substantially impervious to X-rays, one strip of each sectorbeing radial With respect to the aXis about" which the disc is mountedto turn, and the parallel to such radial strip.

3. An AX-ray screen consisting of a disc mounted to turn and built u pof a plurality of sectors each comprising a series of spaced strips madeof a material substantially impervious to X-rays, .the central strip ofeach sector being radial'with respect to the axis about which the discis mounted to turn, and the other strips of the same sector beingparallel to such central strip.

' an angle to the directions of the layers in the neighboring iields'. Y

5. An X-ray screen consisting of a disc mounted to turn and composed ofa plurality of sectors forming individual iields, each ofsaid sectorscomprising parallel layers oi a material substantially impervious to X-rays alternating With parallel layers of-a material substantiallypervious to k-rays,y

all of said layers being disposed at right angles to the plane of thescreen, andthe Ylayers of each individual sector extending ina directionat an angle to the directions oi"- the layers 1n the neighboringsectors.'

6. An X-ray screen consisting of a. body mounted to turn and composed ofaV plurality of individual fields, each of such lields comprising spacedparallel strips of a material substantially imperviousto X-rays, saidstrips being arranged' edgewise withv respect to a plane of rotation,and the strips ot each individual field extending ina'direction at anangleY to the directions of the strips in the neighboring fields. i Y

ln testimony whereof lA affix my signature. 1

FRIEDRICH JANUS.

